Embodiments disclosed herein relate generally to an apparatus and method of delivering a fluid into a wellbore.
Hydrofracking, commonly known as fracking, is a technique used to release petroleum, natural gas or other substances for extraction from underground reservoir rock formations. A wellbore, drilled into the reservoir rock formation, and into which treatment fluid is pumped, causes fractures and allows for the release of trapped substances produced from these subterranean natural reservoirs. Current wellhead fracking systems utilize a process wherein the treatment fluid is pre-mixed prior to being pumped to the required wellhead pressure. This means the fracking pumps are handling a treatment fluid mixture that contains sand and/or other abrasives as well as possibly a host of chemical additives. Use of such treatment fluid mixtures has been shown to cause significant deterioration of the fracking pumps, eventually leading to the need for their repair or replacement. This means at each wellhead site a significant number of spare parts or complete spare fracking pumps are required to be on hand to assist in rapid repair and/or switch out to maintain the ability to continue the fracking process. This large number of spare parts and/or complete fracking pumps is a cost carried by the fracking company as well as requiring significant space, where space may be at a premium. In addition, repair and/or replacement delay times are also a loss to the fracking company. The loss of a fracking pump during operation can result in the loss of the entire fracking operation on that section of the well; a significant economic loss to the well developer.
Fracking pumps are typically mechanical based pumps that utilize pumping solids, especially solids such as sand, as well as some chemicals. Mechanical pumps have inherent issues as the solid materials can rapidly damage the mechanical pump components, such as pistons, through abrasion and erosion and the chemicals can corrode the pump materials. Mechanical pumps rely on the motion between two parts that move relative to each other with close tolerances and and/or sealing features between the two parts. It is in this boundary where small solids, such as sand, can enter and become trapped. With successive motion, the trapped solid abrades one or both of the two mating parts. In addition as the mechanical pump has mating surfaces that move relative to each other, the choice of materials is limited due to tribology concerns, including friction, lubrication and wear. These tribology concerns may preclude material choices that could withstand chemical attack or erosion. With the use of standard materials in an acceptable pair for tribology, one may not be able to design around erosion, corrosion or have the ability to apply corrosion or erosion resistant coatings. This damage ultimately leads to reduced pressure capability and/or flow rate and when a critical status is reached, the pump requires repair or replacement.
Previous attempts utilized for pumping a treatment fluid at the wellhead of a fracking system have utilized the concept of splitting the wellhead treatment stream into a pure water stream or clean stream (defined as a fluid that does not erode or corrode) and a dirty stream that contains the abrasives and chemical content. Systems utilizing this split wellhead treatment stream are commonly known as split-stream systems. Known split-stream systems utilize conventional mechanical pumps for both the clean stream and to deliver the abrasive/chemical stream. In split-stream systems, there are a number of these mechanical pumps that operate to pump only the clean stream and a second set of pumps that operate with the abrasive/chemical fluid. Due to the fact that there is always a pump that will face the abrasive/chemical stream, the pump will ultimately face the same issue with maintenance penalties. More specifically, in a split-stream system there will remain at least one mechanical pump subjected to the harsh fluid with the associated maintenance penalty, so while the maintenance issue is reduced, it is not solved.
Accordingly, there is a need for an improved pumping system and method for delivering fluid into a wellbore that will reduce wear and tear on the pumping mechanism utilized in the pumping system.